At present, the practical applied display devices mainly comprise Cathode Ray Tube (CRT), Liquid Crystal Display (LCD), Vacuum fluorescent devices (VFD), Plasma Display Panel (PDP), Organic Light-Emitting Device (OLED), Field Emission Display (FED) and Light-Emitting Device (LED).LCD, OLED, etc, have been gradually replaced the CRT displays.
Organic Light Emitting Diode (OLED) is a flat panel display technology which has great prospects for development. It does not only possess extremely excellent display performance but also properties of self-illumination, simple structure, ultra thin, fast response speed, wide view angle, low power consumption and capability of realizing flexible display, and therefore is considered as “dream display”. It has been favored by respective big display makers and has become the main selection of the third generation display element.
Compared with the LCD display devices, the OLED display devices possess advantages of being thinner, lighter, wide view angle, active lighting, continuous adjustable light color, low cost, fast response, low power consumption, low driving voltage, wide usage temperature range, simple production process and high illuminating efficiency and possible flexible display, and the investment for the production equipments is far smaller than the LCD. The OLED has earned the great attention of the industry and the scientific community due to its incomparable advantages and beautiful application prospect than other displays.
The OLED can be categorized into two major types according to the driving methods, which are the Passive Matrix OLED and the Active Matrix OLED, i.e. the direct addressing and the Thin Film Transistor (TFT) matrix addressing.
As shown in FIG. 1, the present Active Matrix OLED display substrate comprises a substrate 100, a TFT located on the substrate 100, a passivation layer 300 located on the TFT layer, a flat layer 400 located on the passivation layer 300, an anode 500 located on the flat layer 400, an organic emitting layer 600 located on the anode 500 and a cathode (not shown) located on the organic emitting layer 600. A electrode hole 700 is above a drain 200 of the TFT and penetrates the flat layer 400 and the passivation layer 300 to expose a partial surface of the drain 200. The anode 500 is recessed at the electrode hole 700 to contact the drain 200 for receiving driving signals and controlling the lighting of the OLED. However, as manufacturing the organic emitting layer 600 on the anode 500, the organic emitting layer 600 on the recessed part of the anode 500 can be too thin or even cannot form thereon. If the manufacture of the cathode on the organic emitting layer 600 is proceeded, the short circuit between the cathode and the anode can happen very easily. The current concentration passing the short circuit can stop the current flow through the organic emitting layer 600 and cause issue incapable of lighting of the OLED.